Motor control system



Jan. 11, 1938. cuNNlNGHAM 2,104,972

MOTOR CONTROL SYSTEM Filed July 19, 1935 Wm 3mm Lewis L. Cunningham Snow Patented Jan. 11, 1938 UNITED STATES'PATENT OFFICE MOTOR CONTROL SYSTEM Lewis L. Cunningham, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application July 19, 1935, Serial No. 32,224

11 Claims. (Cl. 172-239) The present invention relates to those systems fluid thermostat 13. This thermostat comprises wherein it is desired to position a device in aca beilows i4, controlling bulb l5 and connecting cordance with the movements of a controlling tube 56. As is well-known in the art, the temmember. perature to which the controlling bulb I5 is sub- One of the objects of the present invention is jected causes variable vapor tension to be mainthe provision of a graduated control system of tained within the bellows l4, tube l6 and control the electrical type in which a single electrobulb l5, all these parts being charged with the magnetic means operates both to control a switch proper amount of volatile fluid suitable for the in control of the electrical motor means of the temperatures to which the thermostat i3 is to graduated control system and to firmly hold respond. The bellows l4 acts upon a control closed a switch which controls such electromagarm H which is pivoted as indicated at IS. A netic means. main spring 19 has one of its ends connected to More specifically, the invention comprehends the control arm I! and its other end connected a system wherein a switch is controlled in any to a suitable support 2 and acts in opposition manner by the conjoint action of an electrical to the pressure created within the thermostat l3 motor means and a controlling member, this so as to counter-act the same. switch in turn controlling electromagnetic means A first double-circuit switching means comwhich not only controls the energization of the prises a flexible arm 2i that carries a pair of motor means but also operates upon its own concontacts 22 and 23 which respectively cooperate trolling switch so as to hold the same firmly with a pair of associated contacts 24 and 25. closed. This switch arm 2! is controlled by the control A further object of this invention is the proarm I! and is herein shown as being directly vision of a graduated control system in which a connected thereto through the medium of a controlling switch is controlled by the conjoint block of insulating material 26. action of a variable controlling force and a var- This first switching mechanism controls a baliable balancing force, the variable balancing anced relay that comprises similar relay coils 30 force being controlled by electric motor means and 3i which respectively cooperate with the which positions a device to be controlled and is legs 32 and 33 of an armature 34 which is pivoted in turn controlled by said controlling switch. at 35. This armature 34 controls a second Preferably, the variable controlling force is a switching mechanism that comprises a flexible variable pressure, such as-steam pressure or the switch arm 36 that carries contacts 31 and 38. pressure generated in a fluid thermostat, and the These contacts 32" and 38 respectively cooperate balancing force is in the form of a spring. Also, with contacts 39 and 40. It will be evident that in the preferred form, the above mentioned conii the relay coil 39 is sufficiently morehighly entact pressure increasing method it utilized. ergized than the relay coil 3i, the armature 34 Other objects reside in the various combinawill rotate counter-clockwise and move contact tions and sub-combinations illustrated in the 31 into engagement with contact 39. Similarly, drawing and contained in the detailed description if the relay Co 3| is sufficienfly more highly and appended claims. I ergized than relay coil 30, the contact 38 will For a more complete understanding of the inbe moved into enga w t Contact vention, reference may be had to the following The energizations of relay coils 3D and 3| are description and accompanying single drawing controlled by the first switching mechanism which is a diagrammatic illustration of one emcomprised by the contacts 22, 23, 24 and 25. The bodiment of my invention. control of the energization of relay coils 30 and Referring to the single drawing, the device to 3-! by these con ac s m y be obt in in ny be controlled is herein illustrated as a valve In sirable manner but is herein shown as being obthat is provided. with a valve stem H which is mined by having bfi Of these relay Coils normalconnected to a rack l2. The variable controlling ly equally energized and by then short-circuiting force, in accordance with which it is desired to one or the other of them. For this purpose, power position the valve I 0, is herein disclosed. as a is supplied to these coils by a step-down transvariable pressure which may be obtained from former 45 having 2. high voltage primary 46 and any source or in any desired manner but in the a low voltage secondary 41. The relay coils 3O particular embodiment of the invention disclosed and 3| are connected in series across this in this application, the variable source of pressecondary 41 by a circuit as follows: secondary sure is shown as being obtained from a volatile 41, wire 48, relay coil 30, wire 49, wire 50, relay tact 48.

coil 3i and wire Eli to the other side of secondary When the relay coils 38 and 3| are thus equally energized, it will be evident that the armature 38 will assume the intermediate position shown in the drawing wherein the switch arm extends straight downwardly. In order to control the operative energizations of relay coils 88 and Si by the first switching mechanism, the switch arm 2i is connected to the junction of wires 58 and by a wire 52. The contact 22 is connected to the lower end of relay coil 32 by a wire and the contact 25 is connected to the lower end of relay coil 38 a wire 54. It will therefore be evident that upon movement of switch arm to the left suficiently to bring contact 20 into engagement with contact 25, the relay coil 38 will be short-circuited by wire 48, wire 52, switch arm 2i, contact 23, contact 25, and wire 58. Similarly, upon movement of switch arm 2i to the right sufiiciently to move contact 2 into engagement with contact 24, the relay coil 3i will be short-circuited by wire 58, wire switch arm 2|, contact 22 contact 24, and wire 53. In this manner, engagement of contact 28 with contact 25 causes operative energization of relay coil 3| by short-circuiting relay coil 38 whereupon switch arm 38 is rotated in a manner to bring contact 38 into engagement with contact d8. On the other hand, engagement of contact 22 with contact 24 operatively energizes relay coil 38 by short-circuiting relay coil 3| whereupon contact 31 moves into engagement with contact 39.

In order to eliminate vibration between the contacts 22 and 24 or contacts 23 and 25 and in order to cause a good firm contact pressure to be established between these contacts upon the lightest engagement thereof, the switch arm 36 carries a fork of insulating material at its lower end, designated 55. The fork 55, switch arm 2|, switch arm 36 and contacts 39 and 48 are so positioned and arranged that the left hand prong 58 of the fork 55 engages the switch arm 2| slightly prior to engagement of contact 31 with contact 39. On the other hand, the prong 51 of the fork 55 engages the switch arm 2| on its other side just prior to engagement of contact 38 with con- In this manner, operative energization of the relay coils 38 and 3| not only causes engagement of the respective sets of contacts 3138 and 38-48 but also either causes contact 22 to be more firmly pushed into engagement with contact 24 or contact 23 to be held more firmly in engagement with contact 25 whereby the relay mechanism comprised by the relay coils and associated armature serves the dual function of controlling a switching mechanism and increasing the contact pressure of the switching mechanism which controls this same relay mechanism.

The valve |8 is driven by a motor mechanism that includes a main shaft 18 which is provided with a pinion 1| that cooperates with the rack l2. This main shaft 18 is coupled to a rotor shaft 12 through a suitable gear reduction indicated generally at 13. Mounted upon rotor shaft 12 is a, pair of induction motor' rotors 14 and 15 with which field windings 16 and 11, respectively cooperate. The energizations of field windings 11 and 16 are respectively controlled by the sets of contacts 31-39 and 38-48. They are also controlled by a pair of limit switches the first of which comprises a switch arm 18 and a switch arm 19 and the second of which comprises a switch arm 88 and a switch arm 8|. The circuit area-eve for field winding 18 is as follows: line wire 82, switch arm 36, contact 38, contact 48, wire 83, switch arm 18, switch arm 18, wire 84, field winding 18 and line wire 85. The circuit for field winding 11 is as follows: line wire 82, switch arm contact 31, contact 39, wire 86, switch arm 88, switch arm 8|, wire 81, field winding 11 and line wire 85.

It will be readily apparent that an increase in the pressure in the thermostat |3 causes movement contact 23 into engagement with contact 25 whereas a decrease of pressure within this thermostat causes contact 22 to engage contact In order to obtain a graduated control, it is necessary to provide some means of causing the switch arm 2| to return to its normal central position. One of the features of this invention is the manner in which this is accomplished. It will be noted that the main shaft 18 of the motorized control mechanism carries a disc 98 that is provided with a crank pin 9|. This cranlc pin is connected to one end of a spring 92 which has its other end connected to the control arm ii. If this disc 98 is rotated in clockwise direction, as viewed from the right, the tension of spring 92 is reduced whereby the pressure in the thermostat l3 is effective to move the right hand end of control arm |1 upwardly. If, on the other hand, the disc 98 is rotated in a counterclockwise direction, as viewed from the right, the tension of spring 92 is increased and the right hand end of control arm I1 is moved downwardly against the pressure within the thermostat l3. This same crank pin 9| operates to engage switch arm 18 and switch arm 80 so as to move these limit switches to open position when the crank pin 9! has rotated a quarter revolution in either direction from the position in which it is shown.

With the parts in the position shown, the temperature to which the control bulb is subjected is at the desired value, the switch arm 2| is in an intermediate position wherefore neither of the relay coils 38 or 3| is short-cin cuited so that switch arm 36 is in an intermediate position. Field windings 18 and 11 are therefore both deenergized. The valve I8 is in a half open position. If the temperature to which thermostat l5 now responds should rise, the right hand end of lever |1 will be moved upwardly against the tension of main spring I9 and balancing spring 92 and switch arm 2| will move to the left. When this increase in temperature is sufficient, contact 23 will be moved into engagement with contact 25. Relay coil 38 will thereupon be short-circuited as heretofore explained so that armature 34 will rotate in a clockwise direction. Just before contact 38 engages contact 48, the prong 51 of fork 55 engages the right handside of switch arm 2| and presses contact 23 more firmly into engagement with contact 25. Instantly that this occurs, the contact 38 is moved into engagement with contact 48 and held in such firm engagement by the action of relay coil 3| which is now operatively energized. Engagement of contacts 38 and 48 energizes field winding 18 by the circuit hereinbefore described whereupon rotor 14 drives the main operating shaft 18, through the reduction gearing 12, in a counter-clockwise direction as viewed from the right whereupon the valve I8 is Opened more widely. The valve 8, for instance, may well control the flow of cooling medium to some device which infiuences-the thermtstat II. This counter-clockwise rotation of main operatlng shaft 18 causes the crank pin 8| to be moved upwardly so that more tension is placed in spring 92. This additional tension counteracts the increased pressure built up in thermostat M whereupon arm IT is returned to its horizontal position and contact 23 disengages contact 25. The short circuit for relay coil 30 is thereupon interrupted so that both relay coils 30 and 38 are again equally energized whereupon switch arm 36 returns to its central position and contact 38 separates from contact to deenergize field windinglfi. The parts now remain in this new position so long as this-new temperature persists.

If the temperature to which the thermostat I3 responds should rise still further, the action above described will be repeated and the valve it? will thus be more widely opened as the controlling temperature increases until such time as the crank pin ill engages switch arm it to move the same from engagement with switch arm id. The apparatus has then reached its limit of motion in this direction and no further valve opening movement may be imparted thereto. i

Whenever the temperature to which thermostat l3 responds falls, the pressure within the bellows it decreases and the balancing spring and main operating spring is are thereby enabled to move the right hand end of control arm i'i down=- wardly. Switch arm it therefore moves to the right. When this decrease in temperature has been sufficient, contact 22 engages contact 2% whereupon relay coil Si is short -circuited so that relay coil lid is operatively energized. Switch arm 36 is therefore moved to the right and the prong 56 engages the left side of switch arm 26 slightly before contacts 3? and engage so that contact 22 is forcibly held in engagement with contact 2d. Contacts 3? and are also firmly held together under the action of relay coil 3d. This engagement of contacts til andfit energizes field winding ill by the circuit heretofore described and the main operating shaft '50 is thereupon rotated in a clockwise direction, as viewed from the right. This clockwise rotation of main operating shaft 10 causes movement of valve ill in closing direction and also causes crank. pin 85 to move downwardly. Part of the tension on the balancing spring 92 is thereby relieved so that the pressure in the thermostat it becomes efiective to move control arm i'i back to its horizontal position wherein switch arm 2i is operated to separate contacts 22 and 2d. Separation of these contacts removes the short-circuit around the relay coil 3i so that relay coils 30 and (H- are again equally energized. Contact 37 thereupon separates from contact 39 and the field winding 11 is deenergized.

Further decrease in the temperature to which the thermostat l3 responds is accompanied by similar closing movements of the valve l0 and these movements may continue until such time as the crank pin ill engages the limit switch arm an and moves the same out of contact with the cooperating switch arm at.

The flexibility of the switch arms 2! and 36 permits the fork 55 to push contact 22 or 23,

as the case may be, into engagement with contact 24 or 25 and still permit of good contact pressure between contacts 31 and 38 or contacts 38 and 4c. Similarly, when the control arm l1 returns to its central position, the flexibility of these arms permits the separation of contacts 22 and 24 or contacts 23 and 25' in spite of the fact that fork 55 is tending to hold such contacts in engagement.

From the foregoing, it will be apparent that by this invention I have provided a novel follow-up means in a graduated control system wherein the follow-up action is carried back to the primary controller instead of some of the intermediate devices. Further, I have provided a novel manner of obtaining an increase in contact pressure between open contacts in a graduated control system which has novelty irrespective of the manner in which the follow-up or balancing is eifected. It will be readily apparent that many changes may be made in the details of construction and arrangement of the parts and I am therefore to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a control system, in combination, a control member, a device to be positioned, electric motor means in control of said device, a switch in control of said motor means, electromagnetic means in control of said switch, a second switch in control of said electromagnetic means and controlled by the conjoint action of the motor means and said control member, and connections between said electromagnetic means and second switch by which the electromagnetic means increases the contact pressure of said second switch.

2. in combination, a control member, a device to be positioned, reversible electric motor means in control of said device, a double circuit switchmeans in control of said motor means, electromagnetic means in control of said switching means, a switch in control of said electromagnetic means and controlled by the conjoint action of said motor means and control member, and connections between said electromagnetic means and switch by which the electromagnetic means operates upon said switch to increase the pressure between the contacts thereof.

3. In combination, a device to be controlled, a control member, electric motor means in control of said device, a switch in control of said motor means, a pair of electromagnetic coils in control of said switch, a double circuit switching mechanism comprising a switch arm and a pair of cooperating contacts in control of said coils and operable to selectively operably energize one or the other of said coils, connections by which said switching mechanism is operated by the conjoint action of said control member and motor means, and connections between said switching mechanism and coils by which operable energization of either of said coils causes the controlling portion of the switching mechanism to be held more firmly in closed circuit position.

i. In combination, a device to be positioned, reversible electric motor means having first and second circuits in control thereof, a double circuit switching mechanism in control of said circuits, a pair of electromagnetic coils in control of said switching mechanism, switching means comprising a switch arm and a pair of cooperating contacts in control of said electromagnetic coils for selectively operatively energizing the same, said coils being operable to increase the pressure between said'switch arm and either of its contacts upon engagement of the switch arm with either of them, a control member, and connections by which the control member and motor means conjointly control the operation of said switching means.

5. 'In combination, a device to be positioned, double circuit electric motor means in control thereof, a pair of oppositely acting electromagnetic coils connected in series across a source of power, a single armature controlled by said coils, double circuit control switching means operable to shunt one or the other of said coils, a second double circuit switching means in control of said motor means, mechanical connections between said armature and both of said switching means, a control member, and mechanical connections between said control member, motor means and first switching means.

6. In a pressure operated control system, in combination, a control arm having a normal position, a source of variable pressure operative upon increase thereof to move said arm in one direction, a variable opposing force operating to move said arm in the opposite direction, electric motor means in control of said opposing force, a device to be positioned also controlled by said motor means, a switch in control of said motor means, electromagnetic means in control of said switch, and a second switch in control of said first switch and controlled by said arm, said electromagnetic means also acting upon said second switch. 7

in a proportioning control system, in com-- bination, a control arm, a variable controlling force operating to move said arm in one dlrec tion, variable balancing force operating to move said arm in the other direction, double circuit reversible motor means in control of said balancing force, a device to be positioned as a result of changes in value of said controlling force controlled by said motor means, a double circuit switching mechanism in control of said motor means, electromagnetic means in control oi switching mechanism, and switching means controlled by said arm in control of said electromagnetic means, said electromagnetic means also operating upon its controlling switching means.

8. In a proportioning control system, in combination, a control arm, a variable controlling force operating to move said arm in one direction, a variable balancing force operating to move said arm in the other direction, double circuit reversible motor means in control of said balancing force, a device to be positioned as a result of changes in value of said controlling force controlled by said motor means, a double circuit switching mechanism in control of said motor means, double coil electromagnetic means in control of said switching mechanism, and switching means in control of said electromagnetic means, said electromagnetic means being arranged to act upon its controlling switching means.

9. In a follow-up system, in combination, a device to be positioned, motor means in control thereof, a control member, a switch in control of said motor means, electromagnetic means, a second switch in control of said electromagnetic means controlled by the conjoint action of said motor means and control member, and means controlled by said electromagnetic means operable to hold said second switch closed and to close said first switch.

16. In a follow-up system, in combination, a device to be positioned, motor means in control thereof, a control member, a switch in control of said motor means, electromagnetic means, a. second switch in control of said electromagnetic means controlled by the conjoint action of said motor means and control member, and a flexible arm controlled by said electromagnetic means arranged to first engage said second switch to securely hold the same closed and then to close said first switch.

11. In a graduated control system, in combination, a device to be positioned, an electric motor control thereof, a switch which energizes said motor when closed, an electromagnetic coil, a control member, a second switch that is closed and opened by the conjoint action of said motor means and control member, circuit connections between said second switch and electromagnetic coil to operatively energize the latter upon closure of said second switch, and mechanical means operated by said coil when operatlvely energized, operative to hold said second switch securely closed and to close said first switch.

LEWIS L. CUNNINGHAM. 

